Tappet



J. E. FISK Dec. 19, 19440 TAPPET Filed Sept. 17, 1945 IN V EN T 0R.

Patented Dec. 19, 1944 TAPPET John Edwin- Fisk, SoutnEucIid, 01m.

Application. September 17, 1943. Serial No. 502,784

6 Claims. (Cl; 123-410) This invention relates to an adjustable length interponent for spaced reciprocating parts, which interponentwill automatically lengthen or shorten to compensate for either change'in the space in. which. itisadapted to operate.

A specific object is to provide an internal combustion engine valve tappet that will automatically adjust itself to allow for the lengthening of the valve due to the heat of the engine, andalso to. lengthen when necessary to take up lost motion or slack which occurs when the valve shortiens because of wear, or shrinkage when cooling.

Another object is to provide a tappet that will automatically adjust itself to compensate for varying. temperatures at different. parts of the enginefr example ina six cylinder engine the valves controlling cylinder No. 3 may operate at greater heatthan those controlling cylinders Nos. 1 or 6..

A further: object of this inventionisto. provide a tappet that will retain a. fixed length during the opening of the valve by its operating cam, but will if necessary, change in length during'the closing of the valve and/ or whenthe valve is. at rest In the conventiona1 valve operating mechanism a cam isused to open the'valve' thru a. pushrod or tappet; As this takes'place the tappet follows the rise of the cam. Asthe top of the cam passes underneath the tappet the tappet momentarily leaves the cam by reason of its momentum. It is again forced into contact with the cam by the valve spring, This takes place at a time when the top of the cam has revolved out of reach and the tappet then contacts a smaller arc of the cam. The comparatively fastfall of the tappet and sudden stop at the end of its fall is utilized to adjust itto itsproper length;

The previously mentioned objects ofthis invention are accomplished by a circular wedge or pair of wedgeshavinga self-locking angle, suspended pendulously from one operating part and engaging another. A weighted part of the wedge'causes it to swing pendulously when stopped suddenly as when the tappet recontacts the cam. This pendulum action rotates the wedge to introduce more clearance into the valve mechanism. A spring tendsto swing the wedge back in a return pendulum stroke which rotates each wedge to take up excess clearance whichhad just been introduced. The above action of adding clearance: and then taking it up takes place at each revolution of the cam shaft, and is very slight with each operatingcycle of the valve mechanism. Pen-dulous. movement is prevented in the upward or valve opening. movement of the tappet by reason of. the combined weight of the. valve and. the force of thevalve spring. exerting a looking action on the relatively divergent locking faces-ofthe Wedge- Other objects and features of the inventionwill become apparent from the. following description relating to the accompanying drawing which shows several preferred forms. The essential I characteristics are summarized in the claims.

Referring to. the drawing, Fig. 1 is a sectional view taken longitudinally thru a. poppet valve mechanism of. an internal combustion'engine in a plane coincident with the valve stem. axis; Fig. 2. is. a longitudinal sectional view thru the tappet taken atrightanglesof Fig.1. as indicated by line 2.2 on Fig. 1. Figs. 3. and 4?. are diagrammatic views. showing the. essential parts in twodifferent relationships. Fig. 5 illustrates this invention as used together with a rocker arm in an overhead valve type of mechanism. Fig. 6 is an end: view of Fig. 5. Fig. 7 is this invention in a. simplified form as used on amushroom type of tappet.

Referring in detail to thedrawing A represents a. portion of an engine block having. a guide B- forstem C. of avalve; The valve has aheadD shown in closed position against the. valve seat. The valve is closed byspring. E. which reacts against washer F fastened to the. valve stem: at one end and againstaportion of the engine block at theother. 'Ihetappet generally indicated at I. may be cylindrical and adapted to slide-in: the guideG; A cam.H-. onra suitablecam shaft raises the valve from itsseat in proper timed relation.- shipto the operation of the engine" thru the intermediacy of the tappet. For reasons which are well knowmit is desirable that the-end play clearance.- or slack between the valve stem and tappet and cam be reduced to aminimum: and/or entirely eliminated.

The; bodyof. the tappet as. shown in Figs. 1 and 2' comprises a hollow cylindrical member 2 having a substantially closed bottom end. 3. The body is closed: at the tones: by' aninsert. or head 4 shouldered: into the: top? of part 2 and heldarigidly by any well known method; as by: welding, brazing,. or cold shrink fit. Thev head 4? has1a central bore 5 for receiving pin. 6 which slides' in the: bore. The upper: end of the pini 5 abuts the lower end of the valve. stem' C and. forms the effective. upper extremity of the: tappet. Thiscooperates with. the lower closed end 3 to. establish the. proper distance. between the. cam and the valverstem;

Thellowerl endof therp'intii bears againsta pair of circular wedges shown in the form of circular discs 7 and 8, having eccentric inner surfaces 9 and is respectively to form wedge elements 7a and 8a of segmental form. A cross pin l I carried by the head 4 pendulously supports the circular wedges along a relatively small contacting area ed portions 103 and 8d of the wedges and swingthem in opposite directions to take up slack. The spring M is provided with two upwardly extending arms Ida whose ends Mb are bent inwardly and are inserted into holes 1c and 8c in wedges I and 8 respectively. The normal action of the spring is to spread and thereby swing the circular wedges outwardly from the axis of the body and upwardly, rotating them to lengthen the interponent as shown in Fig. 3. The momentum of the weighted portions of the circular wedges induced by the downward movement and sudden stopping of the interponent overcomes this spring force and acts to close the spring, as the weighted portions of the wedges move downward as shown in Fig. 4.

The wedging portion of circular wedges la and 8a is solely that which separates the pin 6 from cross pin II and is proportionately counterbalanced by a non-wedging. portion 1b and 8?). Portion id and 8d of each circular wedge is relative- 1y heavier than its opposite side.

The effective range of the wedge is the difference between the thickness of the wedge at its thin side and thick side which also constitutes 180 of its diameter. The spring l4 prevents a full 180 turn of the Wedge and consequently the heavier portion 7d and 8d of each wedge is at all times disposed laterally with respect to axial movement of this device.

A single wedge only is required to obtain results mentioned. A preferred form has two wedges mounted side by side on a common support, and operating in opposite directions. This is illustrated in Fig. 3 and Fig. 4. Fig. 3 shows the relative positions of each wedge when the interponent has lengthened to take up all possible slack. Fig. 4 illustrates relative position of the wedges at maximum lengthening of the valve stem and consequent shortening of the interponent. One advantage of having two wedges is that when rotated in their respective directions, the operated member 6 is rotated by its contact with the wedges. As shown in Fig. 3 the wedge 1 has rotated in clockwise direction while wedge 8 has rotated in counterclockwise direction, which would turn 6 with the front face moving from left to right. It can readily be seen that this turning of 6 lends itself to greater freedom of movement of all the parts by reduction of static friction.

The wedging action operates just as efiiciently in any position, as for example, inverted as shown in Figs. 5 and 6. The rocker arm l6 shown pivoted as at I! is actuated in the usual manner by a push rod l8 at one end. The other end has two parallel arm portions I9 which have aligned holes the Fig. 1 arrangement. Resilient mean in the form of a spring '23 fastened to rocker arm as by screw 24, pendulously rotates the wedge in one direction while the action of the weighted portion of the wedge tends to rotate it in the opposite direction as previously described. Spacers 25 keep the wedge in proper spaced relation to the adjacent faces of the arms I9.

Fig. 7 illustrates a mushroom type of tappet embodying my invention in a modified form. The circular wedge 30 is supported in the manner described as by a cross pin 3|, and arranged, for example, to rotate in a bore extending crosswise of the slot 32 of tappet body 33. Compression spring 3d having an upwardly extending arm 35 acts to rotate the wedge clockwise to take up slack. The action of the weighted portion 31 of the wedge is to rotate it against the spring to provide clearance in the event of valve expansion as already described. The spring 34 may be contained in an axial eccentric bore or pocket 36 opening into the slot.

Spaced parts as used herein means operatively spaced as for example; the parts I 8 and 22 are spaced in Fig. 5,'and also spaced rectilinearly as are the parts C and H in Fig. 1.

I claim:

1. A motion transmitting device adapted for interposition between spaced parts comprisin a body arranged to be guided for movement between the parts, a cross pin carried by the body, a circular wedge pendulously bearing on the cross pin, said wedge being weighted to induce pendulous motion of the wedge by the movement of said body in a manner to cause a variance in the operative spacing effect of said device.

2.. A self-adjusting variable length device for spaced parts comprising a body, arranged for movement in a guide between the parts, a cross pin carried by the-body, a pair of circular wedges suspended for pendulous motion on said pin to cause a change in the length of the device, means to cause relatively opposed pendulous motion of said wedges inone direction and other means for causing relatively opposed pendulous motion of the wedges in an opposite direction.

3. In a slack eliminator a supporting body, a cross pin thereon having a circular surface, a circular wedge having an inner circular surface in tangential contact with the circular surface of the pin, a weighted portion of the wedge tending to turn the wedge in one direction about the pin, and means acting on the wedge in a manner tending to turn the same in the opposite direction.

4. A valve tappet mechanism in the form of a rocker arm having a circular cross pin at one end and an annular take up member with an inner circular surface tangentially bearing against the pin and an external surface eccentric to the inner surface for wedging contact with a valve or actuating part thereof, the take-up member being normally so positioned and having its mass so distributed with reference to the axis of the inner circular surface that when the rocker arm is rocked the take-up member tends to turn by pendulous sway in one direction generally about the cross pin, and constantly acting resilient means tending to turn the take-up member in the opposite direction generally about the crosspin.

5. An adjustable device between spaced parts, comprising a body adapted to be guided for movement in the direction of spacing of said parts, a cross pin of circular section rigidly carried on body arranged to be guided for movement between the parts, a wedge supported by the body and contacting one of the said spaced parts, and weighted means, arranged for pendulous sway by the movement of the device, tending to move the wedge in a manner to vary the length of the device.

JOHN EDWIN FISK. 

